Pressure pulsing perpendicular permeability process for winning stabilized primary volatiles from oil shale in situ



Sept 20 1966 n M. G. HUNTINGTON 3 27 PREaSURE PULSLNG PERPENDIGULARPERMEABILITY PROCESS P055 WINNING STABILIZED PRIMARY VOLATILES FROM OILSHA Flled Dec. 13, 1963 LE IN SITU 2 Sheets-Sheet 1 M J an STEAMPRESSURE PSlA ATTORNEYS United States Patent 3,273,640 PRESSURE PULSINGPERPENDICULAR PERME- ABILITY PROCESS FOR WINNING STABILIZED PRIMARYVOLATILES FROM OIL SHALE IN SITU Morgan G. Huntington, Galesville, Md.,assignor to Pyrochem Corporation, Salt Lake City, Utah, a

corporation of Utah Filed Dec. 13, 1963, Ser. No. 330,334 9 Claims. (Cl.1667) This invention relates to improvements in the in situ exploitationof oil shale and other hydrocarbonaceous impregnations and particularlyrelates to the pyrolysis, destructive steam distillation and to theinitial vapor phase catalytic hydrogenation of the volatile matter. Thisinvention further relates to the production of a primary condensate oilwhich is substantially free of reactive hydrocarbon unsaturates and ofoxygeneated organic compounds and which is, therefore, essentiallystable in respect to molecular size.

Although a very great deal of engineering knowledge has been accumulatedin the exploitation of various types of liquid petroleum reservoirs,very little of such conventional oil field experience is immediately anddirectly applicable to the in situ winning of oil from such imperviousand benzene insoluble impregnations as the Rocky Mountain oil shales.

No in situ shale oil recovery process has so far been successfullydemonstrated. A number of retorting systems which involve mining,crushing and heating the shale in the absence of air have establishedthe fact that about two-thirds of the initial calorific value of theshale is slowly converted to condensable oil vapors upon heating to atemperature of about 700 F. and more rapidly converted between 800 and900 F. One-third of the remainder is in the form of permanenthydrocarbon gases and the balance of the original heating value isretained as a coke polymer in the calcined host. About 300 B.t.u. ofheat is absorbed per pound of shale during the processes of pyrolysisand of destructive distillation above 800 F. but below the temperatureof carbonate destruction which begins above 1150 P.

All grades and types of shale oil which have so far been extracted fromRocky Mountain oil shales by potentially large scale processes, otherthan those methods disclosed by the present inventor, are less valuablethan commercial grades of petroleum because of the lower gasoline yieldand because of excessive processing and investment costs. The inferiorquality of all previously produced shale oil is due particularly to theaverage high molecular weight of compounds formed in such oils byintermolecular reaction subsequent to pyrolysis and distillation andwhich have been allowed to condense from the vapor phase without priorcatalytic hydro-stabilization.

While it is well known that kerogen, the impregnating hydrocarbonaceoussolid material which occurs in the Rocky Mountain magnesium marlscommonly called oil shales can be largely converted to benzene-solubleliquids by heating, a second and a very serious problem of physicalrecovery remains to be solved. In order to extract fluids fromimpregnated rock hosts through bore holes drilled therein, twoconditions must be met as is the case in all oil field practice: (1) Theimpregnated material must be permeable to the fluid, and (2) some kindof driving and/or displacing force, such as gas, Water or gravity, mustalready exist in the reservoir or it must be artifiicially supplied.

Rocky Mountain oil shale is an impervious and impermeable laminarsequence of magnesium marlstone containing very finely divided grains ofhydrocarbonaceous solids which are petrographically similar to certainconstituents of cannel and boghead coals. Oil shale resembles darkcolored marble and has a hardness of about five on Mohs scale, which isabout as hard as window glass. Its shear strength perpendicular to thebedding planes is 3000 to 4600 pounds per square inch, while parallel tothe bedding planes, its shear strength is only 900 to 1800 pounds persquare inch. Its tensile strength is 340 to 800 pounds per square inch.

The hydrocarbonaceous matter called kerogen is a mixture of amorphous,structureless solids ranging in color from yellow to brown or black.Occasional identifiable pollen grains, spores and microfos'sils areembedded in the organic matter. Only about 15 percent of it is solublein common solvent such as benzene at moderate temperatures andpressures. Despite extreme variation in richness of the various beds,the composition of kerogen is fairly constant as is represented by thefollowing data:

It should be noted that part of the kerogen bears a remarkable and closeresemblance to the petrographic constituents of certain high volatilecoals. (Compare Bureau of Mines Technical Paper 642.) This is notunexpected since geologically, the origins of oil shale and coal aresimilar in that they are both fresh water deposits and the organiccontent of each is the result of vegetable matter decaying andcoalifying in place.

Following the destructive distillation of oil shale at 800 F.900 F., theporisity of the calcine ranges from 15 to 40 percent. Because theprimary mineral matter (chiefly volcanic dust) has an average grain sizebetween 0.5 and 50 microns, the pore size is very small, being for themost part between ten and one-tenth microns. Obviously, this host rockcan be considered permeable only to gases and vapors at low pressuresand to liquids only at very high differential pressures. I

Oil recovered from oil shale by destructive distillation retains most ofthe oxygen, sulfur and nitrogen oc curring in the original kerogen andthese elements, for the most part, are found in chemically functionalgroups, attached to what otherwise would be pure hydrocarbon molecules.Because of the disproportionating reactions of thermal cracking whichaccompany pyrolysis, about half of the hydrocarbon molecules in typicalshale oil vapors are characterized by at least one double bond due tothe insufliciency of hydrogen. These characteristics produce a highlyreactive mixture of tar acids, tar bases, organic compounds of sulfurand unstable hydrocarbons which combine to form the typical molecularcomplex which is commonly called shale oil.

As disclosed in my Patent 3,106,521, granted October 8, 1963, and in myco-pending application Serial No. 307,162, filed September 6, 1963,shale oil produced by any other means than the inventions thereindescribed is highly reactive and unstable. When allowed to condense fromthe initial vapor phase, the condensate immediately begins to change itsmolecular structure by polymerization of olefins and by intermolecularreaction between olefins, tar bases, tar acids and organic sulfurcompounds. As -a result, re-distillation yields some 50 to 60 percent ofresiduum having a molecular weight in the order of 200 to 5000 and evenhigher and which is solid at room temperature. The distillation of shaleoil by all processes except that of the present invention, my co-pendingapplication Serial No. 307,162 and of my Patent 3,106,521, noted above,produces about 40 percent of light fraction and about 60 percent of veryheavy residuum. The lighter fraction, which boils below 600 F.,invariably consists of 40 to 50% of unsaturated and very reactivehydrocarbons. These olefins, if not saturated by hydrogen immediately,combine with themselves and other hydrocarbon molecules to form highmolecular weight complexes which are not readily covnerted intomarketable products.

It is a principal object of this invention to inject heated hydrogeninto the extracted primary shale oil vapors and to maintain most of theorganic vapors at a sufliciently high temperature to preventcondensation before and while being led over suitable solid catalysts topromote the saturation of olefins into hydrocarbons and to remove allorganically combined oxygen as water vapor and thereby destroy the taracid content of the vapors before condensation occurs; and it isparticularly an object of this invention to prevent subsequent liquidphase polymerization and intermolecular reactions so far as islymerization and intermolecular reactions so far as is possible bycompleting substantial catalytic hydrogenation before allowing thesteam-entrained vapors to condense from the initial vapor phase.

The physical functions of this process invention may incorporate some orall of the controlled rock-parting principles disclosed in my US. PatentNo. 2,969,226 when the object is to exploit a sequence of selectedstrata and to maximize the horizontal area exploited from each borehole.

In order to extract valuable hydrocarbons from oil shale by the in situmeans of this invention, it is first necessary to establish fluid flowof a thermal carrier medium such as hot water and/or steam, through apressure parted and sand fractured plane of weakness between aninjection borehole and one or more production 'wells, as is known in oilfield art. Secondly, it is necessary to preheat the host shale adjacentto the parted seam and the boreholes and conduits to a temperature abovethat at which most all vapors condense but below that temperature atwhich appreciable and rapid pyrolysis occurs. Thirdly, the host rockmust be further heated to a temperature at which the organicimpregnation converts to oil vapors, gas and residual carbon. Fourth,the host rock must become permeable to steam and to oil vapors and togases immediately above and below the horizontal plane made pervious bysand fracturing. Fifth, a driving or extracting force must be providedwhich Will expel the recoverable substances from the host rock, and atthe same time, perform as a displacing medium to effectively prevent there-impregnation of the once-impoverished host. Sixth, the entrainingsteam must be largely condensed at a temperature and pressure at whichthe greater part of the oil vapors remain in the vapor phase in order toreduce the partial pressure of steam before catalysis. Seventh, theinitial oil vapors must be reheated to catalytic temperature, mixed withpreheated hydrogen and led over sufficient catalyst to fix oxygen,nitrogen and sulfur as hydrides and to saturate the more reactiveolefins.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, by way of example, the principle of the invention andthe best mode which has been contemplated of applying that principle.

In the drawings:

FIG. 1 is a schematic view in vertical section through the ground and astrata of oil shale showing injection and production boreholes therein.

FIG. 2 is a flow sheet diagram of the processing of steam entrained oilshale volatiles of this invention.

FIG. 3 is a diagrammatic representation of the pattern of drilling theproduction and injection boreholes.

FIG. 4 is a graph of steam pressure against temperature showing thesteam saturation curve and illustrating the temperature and pressurelimits within which the process operates.

FIG. 5 is a graph of pressure against time illustrating the pre-heatingof the host rock and the pulsating pressure applied to the host by theprocess of this invention.

Referring now to the drawings for a description in detail of the processof this invention, there is shown in FIG. 1 an injection well 10 and aproduction Well 12. These wells are produced by drilling an injectionborehole 14 and a production borehole 16 from the surface of the groundthrough a known strata of oil shale 18.

The wells 10 and 12 will have casings 20 and 24 respectively which areplaced and cemeted at 22 and 26 respectively to be gas tight to justabout the top of the oil shale formation 18 under exploitation.

The oil shale formation 18 will have a number of planes of weaknesswhich may be opened up between the injection well 10 and production Well12 by sand fracturing methods as are known in the art. In theillustration in FIG. 1 there is graphically illustrated a bedding plane29 which has been sand fractured by processes known in the art toprovide a series of horizontal pervious planes tributary between theboreholes. The pressure parting is accomplished by inserting granularmaterial and the planes are held open by the granular material withinthe parted planes as is known in the oil field production practice art.

The borehole 20 has three fluid conduits 32, 34 and 36 thereincontrolled by valves 33, 35 and 37 respectively. Similarly, productionwell 12 has fluid conduits 40, 42 and 44 controlled by valves 41, 43 and45. Fluid is injected through conduit'32 under the control of valve 33,vapors may be withdrawn if desired from conduit 34 under control ofvalve 35 and liquids such as water condensate may be Withdrawn throughdeep pipe 36 by a pump or the like under the control of valve 37. In theproduction well 12, the vapors including steam entrained oil shalevolatiles may pass out conduit 42 under the control of valve 43,additional fluid may be injected if desired through conduit 40 under thecontrol of valve 41 and condensate may be removed through deep pipe 44under the control of valve 45.

After parting the plane of weakness 29, the next step in the process ispre-heating the formation including the sides of the parted plane 29 bypumping hot water at substantially steam saturation temperature inthrough one of the pipes in injection Well 10 and removed through pipe44 in production well 12. Water at a high temperature is used forpre-heating due to the superior heat transfer characteristics of waterover that provided by a gas or vapor such as steam. The water ispreferably at a temperature within the range of 400 to 550 F. That is,the temperature of the Water is above the temperature at which excessivecondensation of the oil entrained vapors in steam might occur. That is,the formation must be pre-heated to a temperature such that the steamand oil entrained vapors would not condense. As shown in the steamsaturation curve of FIG. 4, this would be about 425 at 325 p.s.i.g. Theupper limit of pre-heating by the water is the temperature at whichpyrolysis of the oil shale 18 begins, i.e., in the order of 550 to 600F. It is however desirable to preheat as high as possible withpressurized water as it provides more efficient heat transfer as notedabove.

After the pre-heating step, the hot water is removed through pipe 44 andthe recovery of the volatiles from i the shale formation begins byintroducing superheated steam through pipe 32 under the control of valve33 to raise the temperature of the oil shale in the formation 18 toabout 825, or at least to a temperature sufficient to accomplishpyrolysis or distillation of the kerogen entrained within the shale.

The pyrolyzed shale will leave certain voids and the shortest paths forsteam penetration into the voids are those which extend transversely tothe plane of parting 29, and since the plane of parting is substantiallyhorizontal, the interstices in the shortest path will be perpendicularthereto; hence, the portion of the title, Perpendicular Permeability.

The next step in the process is for promoting permeability and forobtaining an output from the formation above and below the parted planeor seam 29 by a pulsing eflect applied to the superheated steam. This isgraphically illustrated in FIG. 5 wherein the pressure after pre-heatingis pulsed with respect to time so that with high pressure the steampenetrates into the voids and edges of the oil shale formation in thebedding plane and then the pressure is lowered to allow flow out of theformation and on out of the production well. The highest pressure in thepressure pulsing is about equal to rock pressure (which may be roughlyfigured as approximately 1 p.s.i. per 'foot of overburden). The lowestpressure of the pressure pulsing is, in the illustrated example, between325 and 350 p.s.i. which is the minimum system pressure which will allowseparation of vapor phase oils from liquid water in the partialcondenser 46 without execessive condensation of oil vapors. See thesaturation curve of FIG. 4. In essence, the high pressure pulsing is[for first penetrating to open up the tributaries to the plane ofparting and put the oil shale in the vapor phase by pyrolysis while thesecond and lower pressure cycle is to force the steam entrainedvolatiles to the major pervious plane and make the host rock morepermeable for the next penetration by high pressure steam.

The pulsating pressure allows the oil shale entrained vapors and steamto be bled toward the production well 12 by the driving and extractingforce and especially the extracting force of the pressure pulsing steam.

The next step in the process is to separate a certain portion of thesteam entraining the oil vapors from the vapors by condensing theentraining steam at a temperature and pressure sufficient so that theoil vapors remain in the vapor phase. This step is accomplished in orderto reduce the partial pressure of steam before a later step of catalystsand it is necessary that the oil vapors remain in the vapor phase. Thisstep may be accomplished partially in the upper portion of productionwell 24 by cooling the output pipe 42 or may be accomplished asillustrated in a separate condenser shown in FIG. 2.

As shown in FIG. 2, the steam entrained vapors at output pressure andtemperature are taken off line 42 under the control of valve 43 andpassed to a condenser 46. This condenser accomplishes partial steamcondensation at the output pressure and at steam saturation temperatureand the condensed steam is drawn off as water through line 48. As aresult of such condensation of steam the oil vapors exhibit a muchhigher partial pres.- sure while still entrained in some steam atsaturation temperature, are passed through line 50 to heater 52 whereina source of heat is utilized to raise the vapors in temperature to thatbeneficial for a subsequent step of catalysis. This temperature will bewithin the range of 600 F. to 1300" F.

The heated vapors then are removed from the heater through lines 56 andare joined by heated hydrogen 54 and the heated hydrogen and oil shalevapors in the vapor phase are passed to catalysis chambers illustratedschematically at 58. The purpose of catalysis of the oil shale vaporswhile still in the vapor phase is set forth more in detail in myco-pending application Serial No. 307,162, referenced above \and inessence it is so that the olefins may be saturated.

Without prompt vapor phase hydrogenation, conventional shale oil maycontain approximately 40% olefins which combine with each other and withoxygenated compounds to form unmanageable polymers. However, if theshale oil distillate is kept in the vapor phase and hydrogen is addedthereto and vapors are passed through and over a solid catalyst (such assuitably supported cob'alt molybdate or the best solid non-poisoningcatalyst known in the art for the use of saturating olefins in producingstable hydrocarbons) then the beneficial result mentioned above willoccur. This same type of contact catalysis removes organic oxygen aswater vapor almost as readily thereby eliminating tar acids.

The stabilized distillate is then drawn through line 60 and passed to aprimary fractionator 62 of the type known in the art. From the bottom ofthe fractionator 64 may be withdrawn the plus 400 F. fuel oils while thegasoline fraction may be taken off line 66 of the fractionator andpassed to an acid wash to remove pyridine and its homologs and any otherbasic compounds. The 200 F. overhead from the fractionator passes outthrough line 68 to a condenser 70. The condensate from condenser 70passes to a water separator 72 where water is separated from light oils,the water being taken off line 74 and the light oils off line 76. Thepermanent gases from condenser 70 are taken through line 78 to agasscrubber 80 for absorbing most of the carbon dioxide, carbon monoxide, HS and NH These dissolved and combined gases are removed with liquidsthrough line 82 and the remaining permanent gases passed through line 84to a hydrocarbon absorber system 86 to remove the hydrocarbon gasesthrough line 88 leaving only substantially hydrogen to be taken ofl line90 and this hydrogen may then be re-heated by waste heat in the systemand recycled to line 54 to be used in the system.

After one plane 29 has been operated on, the pipes may be moved upwardlya predetermined distance and cement, such as shown in holes 10 and 12 ascement plugs 133 and 135 respectively, may be filled in to cover theexploited seam 29. Then another bedding plane illustrateddiagrammatically in 31 may be opened up by sand fracturing and theprocess repeated on the next adjacent desirable bedding plane. In asimilar manner, plane 27 has already been worked and has been sealed offas shown by the cement 133 and 135. The system will not leak substantialamounts of the pre-heating hot water or the driving and entraining steamdue to the nature of the oil shale which is quite hard and impermeablein its natural state. Where sealing of pervious zones becomes necessary,conventional methods are applicable.

The arrangement of production and injection wells 12 and 10 shown inFIG. 3 is one possible arrangement drilling on .a hexagonal patternwherein each of the injection wells drives the distilled steam entrainedvapors toward any one of the six production wells by selective valvingarrangements.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to the preferredembodiment, it will be understood that various omissions andsubstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in the artwithout departing from the spirit of the invention. It is the intention,therefore, to be limited only as indicated by the scope of the followingclaims.

What is claimed is:

1. An in situ process for winning oil shale from an oil shale formation,the formation including a production bore hole and an injection borehole drilled therein, as well as a path of lateral fluid communicationthrough the otherwise impervious oil shale between the production andinjection bore holes, the process comprising;

(a) preheating the oil shale adjacent the path of lateral fluidcommunication with hot water to a temperature just below that at whichpyrolysis of the oil shale begins,

(b) introducing superheated steam under pressure into the path oflateral fluid communication through the injection bore hole,

(c) cyclically varying the superheated steam pressure between the limitsof rock pressure and a lower pressure sufiicient to prevent undue steamcondensation,

(d) removing steam and oil shale entrained vapor from the productionwell, and

(e) treating the removed steam and oil entrained vapor after firstreducing the partial pressure of steam by contact catalysis in thepresence of hydrogen.

2. An in situ process for winning oil shale from an oil shale formationhaving a production well and an injection well extending therein, theprocess comprising;

(a) establishing a path of lateral fluid communication between theinjection well and the production well through the oil shale formation,

(b) introducing steam under pressure and at a temperature and insufficient quantity to cause plyrolysis of the shale into the path oflateral fluid communication from the injection well,

() cyclically varying the pressure of the steam in the path of lateralfluid communication,

(d) removing steam and oil entrained vapors from the production well,

(e) reducing the partial pressure of steam in the removed vapors withoutcondensing the oil shale vapors, and

(f) treating the oil shale vapors in the presence of hydrogen by contactcatalysis to stabilize the product .by saturating olefins.

3. A process as defined in claim 2 further comprising heating the oilshale vapors to .a temperature beneficial to catalysis before thecontact catalysis step and also preheating hydrogen prior to contactcatalysis.

4. A process as defined in claim 2 further comprising pre-heating thepath of lateral fluid communication through the shale by hot water priorto introducing steam.

5. A process as defined in claim 4 wherein the preheating isaccomplished at a temperature just below where pyrolysis of the oilshale begins, in the order of 550 F.

6. A process as defined in claim 5 wherein the approximate limits of thecyclically varying pressure are rock pressure and a lower pressuresufficient to prevent undue steam condensation.

7. An in situ process for winning stabilized primary volatiles from oilshale by pressure pulsing techniques comprising; providing at least oneinjection well and one production well, pressure parting a bedding planein the in situ oil shale formation between the injection and productionwells, pre-heating the formation on the sides of the parted plane to atemperature between a lower temperature at which there would beexcessive condensation of steam and oil entrained vapors and an upperlimit at which pyrolysis of the oil shale formation begins, furtherheating the oil shale adjacent the parted plane after said pre-heatingwith superheated steam injected into the oil shale via the injectionwell to a temperature suflicient to cause pyrolysis of the host oilshale, cyclically varying the pressure of the superheated steam to openup tributaries perpendicular to the plane of parting and volatilize theoil shale and to displace the steam and make the host formationpermeable, bleeding the steam and oil 5 shale entrained vapors outthrough the production well, condensing at least some of the entrainingSteam t a 8 temperature and pressure such that the entrained oil vaporsremain in the vapor phase in order to reduce the partial pressureofsteam, re-heating the vapors after the condensing step to a temperaturebeneficial for catalysis, and accomplishing contact catalysis on the oilshale vapors in the presence of heated hydrogen.

8. An in situ process for winning stabilized primary volatiles from oilshale by pressure pulsing techniques comprising drilling at least oneinjection and one production well, pressure parting and holding open abedding plane in the oil shale formation between injection andproduction wells, pre-heating the formation on the sides of the partedplanes by means of hot water to a temperature between the lowesttemperature in which there would be excessive condensation of oil, andan upper temperature at which pyrolysis of the oil shale begins, in theorder of 550 F., removing the pre-heating hot water, further heating theoil shale adjacent the parted plane after said pre-heating by injectingsuperheated steam into the oil shale via the injection well at atemperature suflicient to cause pyrolysis of the host oil shale, in theorder of 850 F. upwards, cyclically varying the pressure of thesuperheated steam between an upper pressure equal substantially to rockpressure and a lower pressure sutficient to prevent undue steamcondensation, thereby open up tributaries perpendicular to the plane ofparting, pyrolyze the oil shale, and then displace the steam and makethe host rock permeable, driving the steam entrained vapors out throughthe production well, condensing enough of the steam from the steamentrained vapors at the output pressure and saturation temperature tosignificantly lower the partial pressure of steam in the vapor mixture,reheating the vapors to a temperature beneficial to catalysis, andaccomplishing contact catalysis on the reheated vapors in the presenceof hydrogen.

9. An in situ oil shale process as defined in claim 8 wherein there area plurality of production wells for each injection well.

References Cited by the Examiner Craig et al 166-40 5 CHARLES E.OCONNELL, Primary Examiner.

1. AN IN SITU PROCESS FOR WINNING OIL SHALE FROM AN OIL SHALE FORMATION,THE FORMATION INCLUDING A PRODUCTION BORE HOLE AND AN INJECTION BOREHOLE DRILLED THEREIN, AS WELL AS A PATH OF LATERAL FLUID COMMUNICATIONTHROUGH THE OTHERWISE IMPERVIOUS OIL SHALE BETWEEN THE PRODUCTION ANDINJECTION BORE HOLES, THE PROCESS COMPRISING; (A) PREHEATING THE OILSHALE ADJACENT THE PATH OF LATERAL FLUID COMMUNICATION WITH HOT WATER TOA TEMPERATURE JUST BELOW THAT AT WHICH PYROLYSIS OF THE OIL SHALEBEGINS, (B) INTRODUCING SUPERHEATED STEAM UNDER PRESSURE INTO THE PATHOF LATERAL FLUID COMMUNICATION THROUGH THE INJECTION BORE HOLE, (C)CYLICALLY VARYING THE SUPERHEATED STEAM PRESSURE BETWEEN THE LIMITS OFROCK PRESSURE AND A LOWER PRESSURE SUFFICIENT TO PREVENT UNDUE STEAMCONDENSTATION, (D) REMOVING STEAM AND OIL SHALE ENTRAINED VAPOR FROM THEPRODUCTION WELL, AND (E) TREATING THE REMOVED STEAM AND OIL ENTRAINEDVAPOR AFTER FIRST REDUCING THE PATIAL PRESSURE OF STEAM BY CONTACTCATALYSIS IN THE PRESENCE OF HYDROGEN.